This invention relates in general to a process for treating aqueous waste. More particularly, this process involves treating a copper plating waste stream, a copper rinse stream, and a copper waste stream resulting from chemical mechanical planarization (CMP).
Chemical mechanical planarization (CMP) is a new method of applying copper to semiconductors. In fact, using copper to make semiconductors is new to the industry. Currently, because CMP is a new process, copper waste is merely drummed and shipped off. Similar wastewater created in other industries, such as the plating industry or the printed circuit board industry, generally is treated in an electrowinning process to remove copper. The disadvantage with such a process is that, because particles suspended in the copper CMP wastewater are not removed before the electrowinning process, the separated copper is impure. Another disadvantage with electrowinning the copper CMP wastewater is that the concentration of copper may be too low for effective electrowinning. Still further, utilizing accepted techniques, multiple streams from various processes are not currently treated in an interdependent system.
Other methods of removing metals from wastewater include precipitation of the metals as their oxides, as is well known in the art. The precipitated metals are removed from the water by filtration methods such as bag filtration, ultra filtration, or microfiltration. However, such methods suffer from the fact that they can produce a hazardous sludge, which has no value, and that they do not remove any metals which remain soluble. In fact, disposing of hazardous sludge costs more than disposing of typical sludge due to its hazardous nature.
Thus, a process for treating wastewater containing copper CMP particles is needed which can overcome the above disadvantages. Specifically, a process is needed that will separate impurities from the copper CMP wastewater before the electrowinning step of the process. In addition, a system that is able to simultaneously treat waste streams from copper plating, copper rinse, and copper CMP processes is also needed. Furthermore, a process which does not produce a hazardous sludge would be preferable. In addition, a process which recovers the copper in a form which has value, such as metallic copper, would be preferred.
It is an object of the present invention to provide a process for treating aqueous waste containing copper CMP particles that allows basically pure copper to be recovered from the wastewater.
Another object of the present invention is to provide a process for simultaneously treating a copper plating waste stream, a copper rinse stream, and a copper waste stream resulting from chemical mechanical planarization.
It is another object of the present invention to provide for treating aqueous waste from a variety of sources including wastewater created by a chemical mechanical planarization process.
According to the present invention, the foregoing and other objects are achieved by a process for treating aqueous waste from copper plating, copper rinsing, and copper CMP processes. Another aspect of the present invention is a system for performing the above-described process.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned from practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.